Have a hardshell sphere and take out all the air so there exists a vacuum. The shell should be strong enough to keep the shape of the sphere and the sphere should be big enough so that it will act as a balloon and reach to the upper atmosphere.

Yes, I've heard of that. The idea is quite old, going back several centuries. As my memory serves me (keep in mind, my memory is a whispy thing), an old woodcut depicts workers draining mercury from a copper sphere, to achieve a vacuum inside. Unfortunately, any existing substance that is strong enough to resist being crushed by air pressure would be too heavy to float in the air.

On some site I once saw a proposal for some sort of "tensile spheres" where you have a bunch of inflated balloon-spheres filling up an innertube shape, like peas in a pod. Then you stack a bunch of such innertubes of differing radii, so that they form a hollow spherical shell, which you then wrap another skin around. Apparently, you can vacuum out all the air from everything but the original balloon-spheres, and you could have an air-supported hollow shell.

I've read that newer research into vacuum-lift or vacuum-buoyancy could make use of foam nacelle structures with hollow cores.

Any way I thought if you tacked it like a 3D bridge, then some interesting structures might come out of it.

I imagine a structure divided into cells like that of a soccer ball, and the cells being mad up of frames and some kind of cloth. And the cloth being supported in the middle of the cells by suspension bridge techniques. The structure would be light, but would it be light enough? And the materials would have to be super light and super strong.

I imagine a structure divided into cells like that of a soccer ball, and the cells being mad up of frames and some kind of cloth. And the cloth being supported in the middle of the cells by suspension bridge techniques. The structure would be light, but would it be light enough? And the materials would have to be super light and super strong.

Yes, I've heard of that. The idea is quite old, going back several centuries. As my memory serves me (keep in mind, my memory is a whispy thing), an old woodcut depicts workers draining mercury from a copper sphere, to achieve a vacuum inside. Unfortunately, any existing substance that is strong enough to resist being crushed by air pressure would be too heavy to float in the air.

What about a carbon nanotubes?

_________________“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.” -Anonymous

Graphene is uniquely impervious to gas molecules. It has already been used to create the world's first single molecule balloon, having a skin thickness of only a single atom.

That kind of material could be used to make spacesuits, spaceships, domes, etc that would be totally airtight, because you could use billions of molecular layers of the stuff to keep things airtight. And of course it's obviously of intense interest for electronics.

Nanotubes are great, but in my opinion, graphene is the real story that everyone should first be looking at. If any material could be used to make a hard-shell balloon, it would be graphene. That's one material that will change the world in many ways.